Math
Science
28 rabbit holes · 20 people exploring
Common starting questions
- Why was the four color theorem proof so controversial?
- If the forecast said 70% rain and it didn't rain, was it wrong?
- Why did Perelman refuse the Millennium Prize?
- Is the Dunning-Kruger effect real?
- How do speedrunners manipulate randomness?
Rabbit holes
- the four color theorem was the first big proof nobody could check by hand
Henrik Larsen · 5 sources
- Brier scores, or how to grade a weather forecast
Ryo Nakamura · 5 sources
- finally understood backprop thanks to 3blue1brown
The visuals make it click in a way textbooks never did for me. Rosenblatt's perceptron in 1958 was hyped as basically an electronic brain by the New York Times.
Arjun Pillai · 5 sources
- finally watched the 'parallel universes' video
The A Button Challenge: collect stars pressing A as few times as possible. The explanation for one 'half an A press' route involves building up speed for hours so Mario can reach copies of the level that only exist because of how positions get stored. Understood maybe 60% of it and loved all of it.
Callie Sutherland · 5 sources
- flights to Asia go over Alaska because the map is lying
Assumed it was an airspace thing. It's just that a straight line on a flat map isn't the shortest path on a sphere.
Alistair Grant · 5 sources
- a hobbyist found the 'einstein' tile
David Smith, a retired print technician who liked playing with shapes, found the 'hat' in late 2022 and got in touch with mathematicians. A few months later came the 'spectre', which doesn't even need mirror images of itself. 'Einstein' here is German for 'one stone'.
Kate Lindqvist · 5 sources
- the bar scene in A Beautiful Mind isn't a Nash equilibrium
In the movie the guys all agree to ignore the blonde so nobody blocks anyone. But if everyone else is ignoring her, your best move is to go talk to her, so it's not an equilibrium at all.
Wren Abernathy · 6 sources
- how do we know the oldest people were really that old?
Calment's 122 years is the record. In 2018 two Russian researchers argued her daughter had taken over her identity decades earlier. Most gerontologists who examined the evidence disagree, but it sent me into how ages get validated at all.
Milan Popović · 6 sources
- the mathematician who turned down a Fields Medal and a million dollars
Kate Lindqvist · 6 sources
- the first numerical weather forecast was done by hand and was spectacularly wrong
During WWI, while driving ambulances in France, Richardson worked out a six-hour forecast for a patch of central Europe by hand. It took weeks and predicted an absurd pressure change. But the method was basically right; the starting data needed smoothing. He also imagined a 'forecast factory' of 64,000 human computers in one giant hall.
Tomás Rinaldi · 6 sources
- 0x5F3759DF
The famous magic number in the Quake III source, with the very honest comment next to it. It wasn't even invented at id; people traced it back to earlier graphics work.
Ludovica Ferri · 6 sources
- the Dunning-Kruger graph everyone shares isn't from the paper
The 'Mount Stupid' curve, where confidence spikes at low knowledge, is a meme, not a figure from the 1999 paper. The actual result: people in the bottom quartile overestimated their scores a lot, and people at the top slightly underestimated theirs.
Dev Malhotra · 5 sources
- fell into Fermat's Last Theorem on a Sunday
Fermat wrote in a margin around 1637 that he had a marvelous proof that didn't fit. It took until 1994. Wiles worked on it mostly in secret for about seven years.
Tomás Rinaldi · 7 sources
- Indiana almost legislated the value of pi in 1897
An amateur mathematician convinced he'd squared the circle offered his 'discovery' to the state for free. The bill passed the Indiana House unanimously. A Purdue math professor who happened to be at the statehouse that week talked the senators out of it.
Wren Abernathy · 5 sources
- the algorithm that matches doctors to hospitals also matches kidneys
The 1962 paper is short and readable. The surprising part is that hospitals had already been running basically the same algorithm for a decade without anyone calling it a theorem.
Wren Abernathy · 6 sources
- how a paper about precognition kicked off psychology's replication crisis
In 2011 a respected social psychologist published nine experiments in a top journal suggesting people can sense the future. The methods were completely standard. That was the problem: if standard methods could 'prove' precognition, what else were they proving?
Sara Lindt · 6 sources
- I lost an argument about the Monty Hall problem, then lost it again
Switching wins 2/3 of the time. I knew that! I still couldn't explain it at dinner until we played it with three cards about 30 times.
Milan Popović · 6 sources
- why 60 minutes and 24 hours
60 divides by 2, 3, 4, 5, 6, 10, 12, 15, 20 and 30. The Babylonians had good taste. Decimal time is the funniest failed reform.
Yuki Tanabe · 4 sources
- how speedrunners make their own luck
Pablo Serrano · 5 sources
- Gödel, and why 'this statement is unprovable' isn't a cheap trick
An Bui · 6 sources
- the Soviets built a ternary computer
Setun used balanced ternary (−1, 0, +1) instead of binary. About 50 were built in the 1950s-60s. Balanced ternary makes negative numbers and rounding really elegant.
Callie Sutherland · 5 sources
- fairy circles might be a Turing pattern
Termites or plants competing for water? The water-competition explanation produces exactly the kind of evenly spaced pattern Alan Turing described in 1952. Both camps are still arguing.
Grace Whitfield · 5 sources
- every Pac-Man ghost has its own targeting rule
Blinky aims at your tile. Pinky aims four tiles ahead of you. Inky's target uses both your position and Blinky's. Clyde chases until he gets close, then wanders off to his corner. Four tiny rules and it feels like they're coordinating.
Sol Herrera · 5 sources
- Collatz: a problem a kid can understand and nobody can solve
Take a number. Even: halve it. Odd: triple it and add one. Every number anyone has tried ends at 1. Erdős supposedly said mathematics wasn't ready for problems like this.
Omar Haddad · 6 sources
- BB(5) = 47,176,870, proven by an online collaboration
Among all 5-state Turing machines that eventually halt, what's the longest any of them runs? 47,176,870 steps. Proven in 2024 by a mostly volunteer online group, with the proof checked in Coq.
Wren Abernathy · 5 sources
- why roman numerals have no zero
Matteo Rossi · 5 sources
- you can cut a ball into five pieces and reassemble two balls
Wren Abernathy · 6 sources
- 1729 and Ramanujan
Hardy visited him in hospital and said his taxi's number, 1729, seemed rather dull. Ramanujan said no, it's the smallest number you can write as the sum of two cubes in two different ways. 1³ + 12³ = 9³ + 10³.
Nikolai Volkov · 6 sources